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Discussion Starter · #1 ·
Hello all,

I have recently purchased a second hand Nilfisk P160.1 pressure washer. Upon testing the unit, I discovered it was leaking water from the start/stop valve quite badly, but other than that the unit appeared to be working fine (pump and motor working as it should). I disassembled the start/stop valve and found out that there was a crack in the center of the plastic nut that is holding everything in place.
The solution seemed to be simply ordering a new start/stop valve and replacing the nut to stop the leak. I've done that, but after replacing the valve, the pressure washer did not function as it should: the microswitch was continuously forced in the off position, causing the motor not to run.

I've disassembled the start/stop valve again to see if everything was moving freely, and it seemed to be able to do so. Also I made sure that the microswitch was attached to the valve properly.

As a final test (to check the rest of the functionality of the machine), I decided to remove the microswitch and put it in the on position manually, while keeping the lance handle pressed in, to avoid building up excessive pressure in the pump. Now the pressure washer seemed to be functioning properly (although pressure dropped a couple times, but this could be due to air in the system). However, after about 10 seconds, the brand new nut from the start/stop valve was blown out of its hole by force, completely stripping all the threads of the plastic nut.

I was quite surprised by this and in hindsight think that this have caused the first valve to fail as well.

I have now completely disassembled the pump, but cannot see any clear faults (everything appears to be fairly clean inside). Does anyone here knows what might be the reason that excessive pressure builds up at the start/stop valve that is so powerful to blow it to pieces?

9038


/Hugo
 

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well the pressure regulator is not working right.
use a gauge and measure the pressure.
 

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Discussion Starter · #3 ·
well the pressure regulator is not working right.
Hi Paul, thanks for your reply. This is the first time I'm working on a device like this. Does the start/stop valve also work as a pressure regulator? Or are there other parts involved that regulate the pressure inside the pump?


use a gauge and measure the pressure.
On what side should the pressure be measured? On the output side of the pump or at the place of the start/stop valve?

I would hate to order a new start/stop valve and immediately blowing that one out again as well.

For clarity, here is an overview of the pump internals.
9041


/Hugo
 

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we measure pressure on the outlet hose.

snap another pix of the pumps other side.
are there numbers and brand on the pump?
not sure if it is ar, cat or any of the other brands of pumps
 
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